The present invention relates to a fluorine-containing adhesive which can be adhered firmly to various substrates of inorganic and organic materials, and relates to an adhesive film and laminated article which are produced by using the adhesive.
Hitherto fluorine-containing polymers have been used for various applications because of their excellent thermal resistance, chemical resistance, weather resistance, surface characteristics (low friction property) and electric insulating property.
On the contrary fluorine-containing polymers are generally insufficient in mechanical properties and dimensional stability, and high in price.
In order to make the best use of merits of the fluorine-containing polymer and minimize its disadvantages, investigations have been made with respect to adhesion of the fluorine-containing polymer to inorganic and organic materials and lamination of fluorine-containing polymer layer.
However the fluorine-containing polymer inherently has low adhesive force, and it is difficult to adhere the fluorine-containing polymer directly to other material (substrate). Even if the adhering is tried by thermo processing, adhesive strength of the fluorine-containing polymer is not enough, or even if the polymer has adhesive force to a certain extent, such an adhesive force is apt to vary depending on kind of the substrate. Thus in many cases, reliability on the adhesive strength of the fluorine-containing polymer has been not enough.
In order to adhere the fluorine-containing polymer to other material, there have been studied mainly the following methods:
1. a method for physically roughening a surface of substrate by sand blasting, etc.,
2. a method for surface-treating a fluorine-containing polymer by sodium etching, plasma treatment, photochemical treatment, etc.,
3. a method for adhering by using an adhesive, and other methods.
With respect to the methods 1 and 2 above, surface-treating steps are required, and the steps are complicated and productivity is poor. Also kinds and shapes of substrates are restricted. The fluorine-containing polymer inherently has low adhesive force, and there easily occur problems with appearance (coloring and flaw) of a laminated article.
Use of an adhesive in the method 3 above has also been discussed. A usual hydrocarbon type adhesive does not have enough adhesive property and its thermal resistance is insufficient. Thus a hydrocarbon type adhesive cannot stand under conditions for adhering of a fluorine-containing polymer, which requires molding and processing at high temperature, and peeling due to decomposition of the adhesive and coloring occur. Since the above-mentioned laminated article produced by using an adhesive also is insufficient in thermal resistance, chemical resistance and water resistance, its adhesive force cannot be maintained due to change in temperature and environment, and the laminated article lacks in reliability with respect to its adhesive property.
On the contrary, adhesion by using an adhesive and adhesive composition comprising a fluorine-containing polymer having functional group are discussed.
For example, it is reported that a grafted polymer prepared by graft-polymerizing, to a fluorine-containing polymer, a hydrocarbon monomer which has carboxyl represented by maleic anhydride and vinyltrimethoxysilane, a residual group of carbonic acid, epoxy or a hydrolizable silyl group, is used as an adhesive (for example, JP-A-7-18035, JP-A-7-25952, JP-A-7-25954, JP-A-7-173230, JP-A-7-173446, JP-A-7-173447) and that an adhesive composition comprising a fluorine-containing copolymer prepared by copolymerizing a hydrocarbon monomer having such a functional group as hydroxyalkyl vinyl ether with tetrafluoroethylene or chlorotrifluoroethylene and an isocyanate hardening agent is cured and used as an adhesive between vinyl chloride and corona-discharged ETFE (JP-A-7-228848).
The above-mentioned adhesive or adhesive composition comprising a fluorine-containing polymer prepared by graft-polymerizing or copolymerizing a hydrocarbon monomer having functional group does not have enough thermal resistance, and thus at the time of processing together with a fluorine-containing resin at high temperature or during use at high temperature, decomposition and foaming occur, thereby causing reduction of adhesive strength, peeling and coloring. In case of the adhesive composition disclosed in JP-A-7-228848, it is necessary to corona-discharge the fluorine-containing resin.
Further it is reported that a fluorine-containing polymer having functional group and prepared by copolymerizing perfluoro(vinyl ether) compound containing sulfonic acid, carbonic acid or derivatives thereof and a fluorine-containing monomer is used for an adhesive and adhesive composition. In the specification of U.S. Pat. No. 4,916,020, there is disclosed a laminated article produced by using, as an adhesive, a fluorine-containing polymer having functional group introduced by copolymerizing a perfluoro(vinyl ether) having sulfonic acid group, carbonic acid group or their derivatives and tetrafluoroethylene. In this laminated article, an inorganic material such as metal is surface-treated with an epoxy resin, etc.
JP-A-7-145362 discloses adhesion between a terpolymer of perfluoro(vinyl ether) having sulfonic acid group, tetrafluoroethylene and perfluoro(alkyl vinyl ether) and metal. An adhesive comprising such a fluorine-containing polymer, in which a sulfonic acid group or carbonic acid group is introduced, has insufficient adhesive property to metal, and since the functional group is strongly acidic, there is a problem of causing corrosion of metal on an adhering surface.
Also carbonic acids are in general easy to decompose at high temperature, and at the time of processing at high temperature and during use, easily cause adhesion failure, foaming, coloring, peeling, etc.
In case where the laminated articles produced by using those adhesives are used for electrical materials, since the above-mentioned functional group is introduced in a fluorine-containing polymer and the polymer is ionic, there is a problem such that electric insulating property is greatly lowered.
Further those polymers generally have high water absorption property, and laminated articles produced by using these polymers as an adhesive have poor water resistance. Also because of high water absorption property, it is not proper to use the laminated articles for applications in the electrical and electronic fields where fluorine-containing polymers are used widely.
An object of the present invention is to solve the above-mentioned problems, and provide a fluorine-containing adhesive which can give firm adhesion directly to substrates such as metal and glass while maintaining excellent characteristics such as thermal resistance, chemical resistance, weather resistance and electric insulating property of a fluorine-containing polymer, and an adhesive film and laminated article which are produced by using the fluorine-containing adhesive.
The present invention relates to a fluorine-containing adhesive comprising a fluorine-containing ethylenic polymer having hydroxyl and prepared by copolymerizing:
(a) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having hydroxyl and
(b) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers having no hydroxyl and being copolymerizable with the component (a).
In the present invention, it is preferable that the above-mentioned fluorine-containing ethylenic monomer
(a) having hydroxyl is at least one of monomers represented by the formula (1):
CX2xe2x95x90CX1xe2x80x94Rfxe2x80x94CH2OHxe2x80x83xe2x80x83(1)
wherein X and X1 are the same or different and each is hydrogen atom or fluorine atom, Rf is a divalent alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having ether bond and 1 to 40 carbon atoms or a fluorine-containing oxyalkylene group having ether bond and 1 to 40 carbon atoms.
Further it is preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (a) having hydroxyl is a fluorine-containing monomer represented by the formula (2):
CH2xe2x95x90CFCF2xe2x80x94Rf1xe2x80x94CH2OHxe2x80x83xe2x80x83(2)
wherein Rf1 is a divalent fluorine-containing alkylene group having 1 to 39 carbon atoms or xe2x80x94ORf2, in which Rf2 is a divalent fluorine-containing alkylene group having 1 to 39 carbon atoms or a divalent fluorine-containing alkylene group having ether bond and 1 to 39 carbon atoms.
Further it is preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (b) having no hydroxyl is tetrafluoroethylene.
Further it is preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (b) having no hydroxyl is a monomer mixture of 85 to 99.7% by mole of tetrafluoroethylene and 0.3 to 15% by mole of a monomer represented by the formula (3):
CF2xe2x95x90CFxe2x80x94Rf3xe2x80x83xe2x80x83(3)
wherein Rf3 is xe2x80x94CF3 or xe2x80x94ORf4, in which Rf4 is a perfluoroalkyl group having 1 to 5 carbon atoms.
Further it is preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (b) having no hydroxyl is a monomer mixture comprising 40 to 80% by mole of tetrafluoroethylene or chlorotrifluoroethylene, 20 to 60% by mole of ethylene and 0 to 15% by mole of other monomer copolymerizable with those monomers.
Further it is preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (b) having no hydroxyl is vinylidene fluoride.
Further it is preferable in the present invention that the above-mentioned fluorine-containing ethylenic monomer (b) having no hydroxyl is a monomer mixture comprising 70 to 99% by mole of vinylidene fluoride and 1 to 30% by mole of tetrafluoroethylene, a monomer mixture comprising 50 to 99% by mole of vinylidene fluoride, 0 to 30% by mole of tetrafluoroethylene and 1 to 20% by mole of chlorotrifluoroethylene or a monomer mixture comprising 60 to 99% by mole of vinylidene fluoride, 0 to 30% by mole of tetrafluoroethylene and 1 to 10% by mole of hexafluoropropylene.
Further the present invention relates to a fluorine-containing adhesive film obtained by molding any one of the above-mentioned fluorine-containing adhesives comprising a fluorine-containing ethylenic polymer having hydroxyl.
Further it is preferable in the present invention that the fluorine-containing adhesive film is one obtained by melt-molding any one of the above-mentioned fluorine-containing adhesives.
Further it is preferable in the present invention that the adhesive film is produced by laminating: a layer of any one of (A-1) the above-mentioned adhesive comprising a fluorine-containing ethylenic polymers having hydroxyl and a layer of (B-1) a fluorine-containing polymer having no functional group in its branched chain.
Further it is preferable in the present invention that the above-mentioned fluorine-containing polymer (B-1) having no functional group in its branched chain is at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride and vinylidene fluoride copolymer.
Further it is preferable in the present invention that a layer of any one of (A-1) the above-mentioned fluorine-containing adhesives and a layer comprising (B-1) at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer and tetrafluoroethylene-hexafluoropropylene copolymer are laminated.
Further it is preferable in the present invention that a layer of (A-1) the above-mentioned fluorine-containing adhesive and a layer comprising (B-1) ethylene-tetrafluoroethylene copolymer or ethylene-chlorotrifluoroethylene copolymer are laminated.
Further it is preferable in the present invention that a layer of (A-1) the above-mentioned fluorine-containing adhesive and a layer comprising (B-1) polyvinylidene fluoride or vinylidene fluoride copolymer are laminated.
Further the present invention relates to a laminated article comprising a layer of any one of (A-2) the above-mentioned fluorine-containing adhesives and a layer of (C-1) an inorganic material.
Further it is preferable in the present invention that the laminated article comprises a layer of any one of (A-3) the above-mentioned fluorine-containing adhesives and a layer of (D-1) an organic material.
Further it is preferable in the present invention that the inorganic material (C-1) is a metallic material.
Further it is preferable in the present invention that the above-mentioned metallic material is an aluminum-based metallic material.
Further it is preferable in the present invention that the above-mentioned fluorine-containing adhesive (A-2) is any one of the above-mentioned fluorine-containing adhesives.
Further it is preferable in the present invention that the above-mentioned metallic material is an iron-based metallic material.
Further it is preferable in the present invention that the above-mentioned fluorine-containing adhesive (A-2) is any one of the above-mentioned fluorine-containing adhesives.
Further it is preferable in the present invention that the above-mentioned metallic material is a copper-based metallic material.
Further it is preferable in the present invention that the above-mentioned fluorine-containing adhesive (A-2) is any one of the above-mentioned fluorine-containing adhesives.
Further it is preferable in the present invention that the above-mentioned inorganic material (C-1) is silicon-based material.
Further it is preferable in the present invention that the above-mentioned inorganic material (C-1) is glass material.
Further it is preferable in the present invention that the above-mentioned fluorine-containing adhesive (A-2) is any one of the above-mentioned fluorine-containing adhesives.
Further it is preferable in the present invention that the above-mentioned organic material (D-1) is a non-fluorine-containing polymer.
Further it is preferable in the present invention that the laminated article comprises three layers of a layer of any one of (A-4) the above-mentioned fluorine-containing adhesives, a layer of (B-2) the above-mentioned fluorine-containing ethylenic polymer having no functional group in its branched chain, and a layer of (C-2) the above-mentioned inorganic material, in which the layer of (A-4) the fluorine-containing adhesive is put between the layer of (B-2) the fluorine-containing ethylenic polymer having no functional group and the layer of (C-2) the inorganic material and forms an adhesive layer.